It violates pure landlord/tenant boundaries and leads tenants to behaviors you don’t want

its more of a behavior not how low the interest are. 

Psychology could benefit in marketing analysis, understanding consumer behavior, etc.

At this point I don't even know if we are projecting economics, I think we are trying to weigh the probability of human behaviors, which is a complete roll of the dice. 

Don’t reward bad behavior .

I have found social media to be very useful when evaluating potential tenant behavior.

I selected a narrow tenant pool segment and have been targeting them for the past 15 years.I've also collected behavioral data on our tenant segment over the years and this is part of the input to our data mining software.

Cameras never fall asleep on the job; you have "eyes" 24/7/365 in all covered areas; the software can generate notifications or emails to key people when an area is entered during specified time periods; the quality allows for generally easy identification of people violating the space and/or HOA rules (generating income from fines while changing bad behaviors).You can try to get the city to  do something with the encampment, but since its not actually on HOA property, it will likely take a LOT of effort to make a difference.

Cash for keys rewards tenant for poor behavior and shows no issues on most credit/background checks. 

They say it’s a sweet dog with no history of bad behavior.